function add_sub_frac3_check()

{

	if(document.forms[0].elements[0].value == "3/4")

	{

		self.parent.top.location="add_sub_frac4.html";

	}

	else

	{

		

		if(document.forms[0].elements[0].value == "9/12")

		{

			alert("Yes, that is correct, but It would like a simplified, mixed number, if you please.");

		}

		else

		{

			alert("No, that's not the correct answer.");

		}

		

	}

	return false;

}



function add_sub_frac4_check(str)

{



	if(str.length > 0)

	{

		if( str.indexOf("hours") == -1 )

		{

			if(str == "1/2")

			{

				self.parent.top.location="add_sub_frac5.html";

			}

			else

			{

				if(str == ".5" || str == "0.5")

				{

					alert("Yes, that's correct, but Elmiro's deals strictly in fractions.");

				}

				else

				{

					if(IsAFraction(str))

					{

						if( ParseFraction(str) == 0.5 )

						{

							alert("Yes, that may be correct, but I think it can be simplified.");

						}

						else

						{

							alert("Nope, that's not right.");

						}

					}

					else

					{



						alert("Nope, that's not right.");

					}

				}

			}

		}

		else

		{

			return add_sub_frac4_check(str.substr(0, str.indexOf("hours")-1));

		}

	}

	else

	{

		alert("Nope, that's not right.");

	}

	return false;

}



function add_sub_frac5_check()

{

	if(document.forms[0].elements[0].value == "3")

	{

		self.parent.top.location="add_sub_frac6.html";

	}

	else

	{

		alert("No, that's not quite right.");

	}

	return false;

}



//fraction functions

function IsAFraction( str )

{

	var isFraction=true;

	if( str.length == 0 )

		return false;



	for( var i = 0; i < str.length; i ++ )

	{

		if( !IsValidChar(str[i]) )

		{

			isFraction = false;

		}

	}

	return isFraction;

}



function IsValidChar( ch )

{

	return ( ch == 0 || ch == 1 || ch == 2 || ch == 3 || ch ==4 || ch ==5 || ch ==6 || ch ==7 || ch ==8 || ch ==9 || ch ==" " || ch =="/" );

}



function ParseFraction( frac )

{

	var toReturn;

	var i;

	for( i=0; i < frac.length && frac[i] != " "; i++ );

	

	toReturn =  eval (frac.substr(0, i));

	

	if(i < frac.length - 1) 

		toReturn += eval (frac.substr(i+1, frac.length));

	

	

	return toReturn;

}